A general discussion of the statistical methods utilized in the development of mathematical models of ultrasonically measured fetal structures and formulas for the estimation of weight is addressed. The strengths and limitations of various types of analysis are described. Factors in the selection of the “best model” are discussed. The quantitative graphic representation of data and generated models is pictured. Applications of models to the clinical assessment of the individual patient are discussed. A scorecard for the evaluation of publications pertaining to fetal growth is presented for manuscript evaluation.